A wide variety of electronic circuit applications require the differential measurement of two (complementary) currents and some prescribed amount of rejection of their common mode components. In some applications, the currents being measured exist in a high D.C. voltage and high D.C. current environment, yet their information content is ultimately to be employed in a low voltage and low current environment, with demanding requirements for accurate amplification and filtering, plus the additional requirement for low idle channel noise. As a non-limiting example, various equipments employed by telecommunication service providers employ what are known as `SLIC`s (subscriber line interface circuits), to interface (transmit and receive) telecommunication signals with respect to tip and ring leads of a wireline pair. Since the length of the wireline pair to which a SLIC is connected can be expected to vary from installation to installation, may have a very significant length (e.g., on the order of multiple miles), and transports both substantial DC voltages, as well as AC signals (e.g., voice and/or ringing), it has been difficult to realize a SLIC implementation that has `universal` use in both legacy and state of the art installations.